Centrifuges



Oct. 18, 1966 R. w. HONEYCHURCH 3,

CENTRIFUGES Original Filed March 14, 1962 4 Sheets-Sheet 1 FIG. 1

INVENTOR ROBERT W. HONEYC RCH ATTOR N EY.

Oct. 18, 1966 R. w. HONEYCHURCH GENTRIFUGES Original Filed March 14,1962 4 Sheets-Sheet 2 INVENTOR.

ROBERT W. HONEYCHU 5H ATTORNEY.

Oct. 18, 1966 R. w. HONEYCHURC H 3,

7 CENTRIFUGES Original Filed March 14, 1962 4 Sheets-Sheet 5 FIG. 3

35 I 7 RM FIG. 4

INVENTOR.

ROBERT W. HONEYCH CH ATTORNEY.

Oct. 18, 1966 R. WHONEYCHURCl-j 3,279,689

GENTRIFUGES Originl Filed March 14, 1962 4 Sheets-Sheet 4 FIG.

R m V m ROBERT w. HONEYC,

H v C ATTORNEY.

United States Patent 3,279,689 CENTRIFUGES Robert W. Honeychurch,Stamford, Conn., assignor to Don-Oliver Incorporated, Stamford, Conn., acorporation of Delaware Continuation of application Ser. No. 179,610,Mar. 14, 1962. This application July 27, 1964, Ser. No. 386,114 12Claims. (Cl. 233-14) This application is a continuation of applicationSerial No. 179,610 filed March 14, 1962 and now abandoned.

This invention relates to improvements in centrifugal machines forseparating a feed mixture or emulsion into at least two distinctoverflow fractions. In one specific embodiment, the invention relates toa three-product centrifuge of the type having two liquid overflowfractions and a solids-carrying underflow fraction.

It is a primary object of the invention to improve the quality of theseparation accomplished in such machines to an extent not attainable inthe prior art.

The invention may be exemplarily incorporated in a three-product machineof the type disclosed in the copending patent application ofHoneychurch, Serial No. 34,303 filed June 6, 1960, now Patent No.3,204,868. In that particular machine, the two liquid overflow fractions(respectively denominated primary and secondary or intermediate)discharge over annular dams at respective opposite axial ends of themachines rotor, and provision is made for returning to the rotor aportion of the underflow fraction discharged from the rotorsperipherally located nozzles and/or for introducing .wash water orcontrol liquid into the rotor. More particularly, this type of machinefeatures a combination of two sets of conduits arranged within therotor, namely a set of overflow conduits for the intermediate orsecondary fraction and a set of return conduits forunderflow returnand/or wash liquid introduction. Both sets of conduits are disposedgenerally radially to connect respective chambers adjacent the rotoraxis to respective fraction zones near the rotor periphery. The inletsof the intermediate fraction overflow conduits are, of course, locatedat an intermediate radial position within the rotor so as to withdraw afraction having a specific gravity between that of the primary overflowand that of the underflow.

During operation of such a machine, underflow material or solids fromthe feed necessarily pass through the intermediate fraction zone on theway to the peripheral nozzles. Therefore, under some operatingconditions and with certain kinds of feed suspension, there is thetendency for some of the solids, especially the fines, to be carriedinto the intermediate fraction overflow conduits along with theintermediate liquid fraction. In particular, this condition of solidscarry-over is aggravated where there is only a minor specific gravitydifferential between the intermediate overflow fraction and the solidsin the underflow or where the rate of intermediate overflow isrelatively large as compared with the rate of the primary overflow.Further, in this type of machine the localized nature of theintermediate overflow inlets in relation to the total periphery of therotor bowl may cause unevenness in the interface between the primary andintermediate fraction with a resultant adverse effect on the quality ofthe separation of the two overflows.

Accordingly, an object of the invention is the elimination of carry-oversolids in the intermediate liquid fraction by providing for special flowconditions and structural improvements in the rotor. Further, an objectof the invention is the improvement of the separation of the primary andintermediate overflow fractions.

To accomplish the foregoing objects, the invention provides peripherallyextensive inlet structures to avoid high velocity or turbulent flow atthe inlets to the inter- "ice mediate fraction overflow conduits andstructure to mini mize the quantity of solids passing in close proximityto these inlets. That is, the intermediate overflow inlets are speciallyconfigured as peripherally elongated apertures of greatercross-sectional area than the corresponding conduits. In this way, theflow of intermediate fraction liquid will have a velocity low enough topromote laminar flow conditions at the conduit inlet. Further, theseelongated inlets are spaced away from the internal rotor surface so thatsolids moving along the rotor surface will not pass closely adjacent tothe inlets and therefore will not be carried over into the intermediateoverflow. With this improved arrangement, solids from the feed mixturewill tend to move rapidly outwardly seeking to settle against thesurface of the rotor bowl. These heavy solids will then slide radiallyoutwardly upon this surface through the spaces under the conduit inletsdirectly into the region of the nozzles for discharge therethrough inthe underflow.

In the preferred embodiment of the invention, the intermediate overflowfraction conduits terminate within the rotor in shallow, flat,fan-shaped or sector-shaped tubes having inlet openings across the fanperiphery. These fan-shaped tubes are disposed obliquely within therotor. in such a manner that the several tubes define a cone-likeconfiguration. As a result of this structural'arrangement, a clarifiedlayer of intermediate fraction liquid will form under the outer externalsurface of the fan-shaped tubes and will pass across the associatedinlet edge or lip for discharge through the overflow conduit.Furthermore, the laminar flow and the resultant quasi-separating-disceffect induced in the shallow fan-shaped tubes are effective toencourage any carry-over solids that may have succeeded in entering theinlet to settle out and build up on the outer internal tube surface tothe returned from the conduit back to the region of the nozzles fordischarge with the underflow.

According to one feature of the invention, the foregoing improvedcentrifugal separating effects induced within the rotor are enhanced bya extension of the inner lip of the elongated inlet to form asubstantial overhang ex tending beyond the opposite or outer lip. Bythis arrangement, lighter solids from the mixture that settle againstthe inwardly facing external surface'of these fan-shaped tubes will tendto slide outwardly thereon to fall toward the nozzles from therespective inner lip extensions at a point beyond the actual inletopening, thus avoiding carryover into the intermediate fraction.

Other features and objects of the present invention will more fullyappear from the following description and appended claims when read inconjunction with the accompanying drawings wherein:

FIGURE 1 is a vertical section of a rotor of a threeproduct centrifugalmachine featuring the novel inter mediate fraction overflow conduits ofthe present invention.

FIGURE 2 is a fragmentary horizontal section taken substantially on line22 of FIGURE 1.

FIGURE 3 is a fragmentary vertical section of the rotor of FIGURE 1showing one of the specially constructed overflow conduits.

FIGURE 4 is similar to FIGURE 3 lbut shows flow lines indicative of theimproved separating operation of the invention.

FIGURE 5 is a detail section of the inlet end of the conduit of FIGURE4.

FIGURE 6 is a vertical section of the conduit of FIG- URE 3 illustratingthe conduit mounting arrangements.

The rotor structure embodying this invention is mounted for rotation ina stationary housing which may be in the form shown in theaforementioned Honeychurch copending application. Such a housingprovides'threeam nular receiving sections spaced axially from oneanother for receiving the underflow fraction from the rotor nozzles andthe two overflow fractions respectively. However, for purposes of thisinvention, the housing itself need not be shown or described.

An example of a rotor structure embodying the invention is shown inFIGURE 1. The rotor includes a rotor bowl which defines an annularcentrifugal separating chamber 11 and has a double cone-shaped body 12,preferably in the form of an integral member, having conical internalwalls or surfaces 12!). Rotor body 12 contains in its outer peripherythe well known nozzles 12a for discharging the solids carrying mixturethat constitutes the underflow. Rotor bowl 10 includes a conicalextension 13 locked to rotor body 12 as by a securing ring 14 having athreaded engagement with the rotor body. The conical extensionconstitutes one constricted end and one overflow dam of the rotor bowland defines an annular overflow-lip 15 for centrifugally discharging theprimary liquid overflow fraction from the bowl.

The opposite constricted end 16 of rotor bowl 10 is closed by a hub 17having a hub rim 17a preferably thread connected as at 18a to the rotorbowl. Hub 17 is securely fastened to a rotor shaft 18 as by a key 19, apair of opposedly arranged conical wedge devices 20 and 21, a lockingwasher 22, and a lock nut 23. A recess 24 provided in the bottom of thehub to accommodate which. closely fits against the upper surface of thehub and extends across channel 27 to sealingly abut the internal surfaceof rotor body 12 as by an O-ring (FIGURE 3). Adaptor ring 29 is fastenedto hub 17 by means of screws 30a.

Ring 29 has a set of return flow passages. 31 spaced aroundthe rotoraxis to communicate with the annular distributing channel 27. A set ofreturn conduits 32 is connected to the respective passages 31 to returnunderflow material and/or control liquid into the region of the nozzles.The conduits are disposed adjacent and substantially parallel to thesurrounding conical internal surface 12b of the rotor bowl. Moreparticularly, each of these conduits 32 comprises a short connector 32athreaded into a respective passage 31 and a much longer free-ended tube32b removably connected to the connector as by suitable coupling meansor a union 32c. Return tubes 32b terminate at a circumferential positionintermediate underflow nozzles 12a.

Ring 29 also has a set of overflow passages 33 spaced around the rotoraxis in alternation with the return passages 31. Passages 33 registerwith overflow ducts 34 provided to extend in a generally axial directionthrough pumping vane 28 of the hub. A set of specially constructed andparticularly shaped conduits 35 are connected to respective overflowpassages 33 and thus to the associated overflow ducts 34.

More particularly, each overflow conduit 35 of the present inventioncomprises a short tubular male connector 36 extending in sealed relation(FIGURE 3) through a respective passage 33 in ring 29 and across annulardistributing channel 27. Connectors 36 are thread-connected as at 37(FIGURE 6) in the associated overflow ducts 34 of the hub. Conduit 35further comprises a sector-shaped or fan-shaped overflow tube 38 formedwith a significantly widened although shallow.

inlet end. As shown in FIGURE 2, the inlet edges or lips of the widenedtube 38 occupy a significant portion of the circumference of theseparating chamber between respective return tubes 32.

purposes fully described below, plate 42 is spaced a relatively smalldistance from .plate 40 (in the order of one to two times the spacingbetween the conventional separating discs of the rotor). An elongatedinlet or mouth 44 is thus formed between lip41 and the opposite portionof plate 42 in the intermediate liquid fraction zone of the separatingchamber 11.

45 (FIGURE 2) to form the tube structure.

The two sector-shaped plates 1 40 and 42 are suitably interconnectedalong their sides;

Conduit 35 further includes a tubular stub 46 secured to the apex end ofsector-shaped tube 38. A coupling means or union 39 detachablyinterconnects stub tube 46 with male connector 36.

Sallow centrifugal separating spaces 360 having a depth in the range ofa% or more are formed between the conduits 35 and the surroundingconical surface 12b of the rotor bowl for-purposes fully describedbelow. The

sector-shaped tubes 38 of these conduits have lugs 36b to brace thetubes with respect to the surrounding rotor wall. Spacer pins 360(FIGURES 2 and 6), unitary with the aforementioned spacer lugs 36b, maybe provided within the sector-shaped or fan-shaped tube to stiffen thewalls thereof against each other.

The rotor structure further comprises an axially extending feedwell 48(FIGURE 1) surrounding rotor shaft 18. The feedwell includes a flaringfoot 49 having enclosed, radially extending feed ducts 51 leading intothe sur.-

rounding separating chamber 11. The feed ducts are separated by internalpumping vanes formed integrally in the feedwell. The flaring-foot isfastened to hub 17 by the aforementioned screws 30:: extending throughthe feedwell pumping vanes. Feedwell 48 has external, longitudinallyextending impeller vanes 52 around which are seated a stack of thefamiliar separating discs 53 confined between a conical face 54 at thebottom of the stack presented by the feedwell flaring foot and a conicalface 55 at the top presented by conical extension 13 of the rotor bowl.Feedwell 48 extends axially outwardly through the primary overflow endof the bowl for receiving the feed mixture.

Finally, at the bottom of the rotor a chamber ring 56 is coaxiallyfastened to the outer annular face 57 of rim 17a as by upwardlyextending screws 58. Chamber ring 56 together with hub 17 constitute acentrally disposed return chamber 59 adjacent to but separate fromseparating chamber 11 of the bowl. Inwardly extending radial pumpingvanes 60 are provided internally on the chamber ring to cause, togetherwith pumping vanes 28 on the hub,

return material or the like to be impelled into return conduits 32 fordelivery in the region of the nozzles.

Chamber ring 56 also has an annular intermediate overflow chamber 61surrounding the central return chamber 59. Overflow ducts 62a in ring 56register with over flow ducts 34 in hub rim 17a. This composite ductarrangement enables the secondary or intermediate liquid fraction fromoverflow conduits 35 to finally discharge over a ring dam 62 secured tochamber ring 56 by the above-mentioned screws 58.

Located in the central return chamber 59 is an auxiliary arrangement ofvertically. extending but horizontally curved blades 64 carried by aterminal ring65 removably fastened as by screws to the outer end of achamber? separating portion 66 of ring 56. These auxiliary blades 64 inturn carry above them a bathe plate 67 spaced axially from terminal ring65 whereby the incoming return material or the like is deflected inradial directions for delivery into the divergent tube members 32 by theconjoint action of the pumping vanes 28 and 60.

Operation The operation of the invention in the above describedthree-product machine can best be described by referring to a type offeed material or slurry consisting of a mixture of three substances ofdifferent specific gravities, for instance, oil as the light fraction,water as the intermediate fraction, and solids (ranging from relativelycoarse particles to fines) as the heavy fraction. When this mixture issubjected to centrifugal separation in a three-product machine, anaqueous slurry of the solids discharges from the nozzles while the waterand oil discharge from the respective intermediate and primaryoverflows. The present invention produces these three fractions cleanlyseparated from one another, and in particular, produces an intermediatefraction of high purity with respect to solids, the potential carry-overof which into the intermediate overflow is averted by the improvedseparating flow conditions induced in the separating chamber by thisinvention.

When the rotor is rotated, the feed mixture or emulsion entering thefeedwell member 48, as indicated by flowlines A, is propelled by theimpeller vanes 50 and is forced outwardly through the downwardlyinclined feed inlet passages 51 into the annular separating chamber 11.There, centripetal force will cause the separation of the separation ofthe mixture into an extreme outer zone of a Water-solids slurry, anintermediate zone of the clean Water fraction, and an inner zone of thelight oil fraction. With proper hydraulic balance established in thecentrifugal system of the rotor bowl, there will be a continuousdischarge of these three fractions. That is, the under.- flow willdischarge through nozzles 12a, the water will discharge as indicated byflowlines C from the ring dam 62 at the rotor bottom, and the oil willdischarge as indicated byflowlines D from extension 13 at the top of therotor structure.

In the exemplary embodiment disclosed, underflow recirculation and/orintroduction of a control liquid into the bowl may be effected forwell-known control purposes such as control of the underflowconcentration and/or control of the location of the above describedfraction zones. As indicated by flowlines B, this underfiow materialand/or control liquid are introduced into the central return chamber 59and are propelled 'by the cooperating pumping vanes 64, 60, and 28through the return conduits 32 for delivery into the extreme outerperipheral zone in the region of the nozzles.

Referring to FIGURES 4 and 5, as the feed mixture enters the separatingchamber 11 there occurs an immediate separation of the coarse or heaviersolids due to the tendency thereof to settle outwardly against theconical bowl surfaces 12b. As indicated by flowlines R-1, these solidsthen slide along the bowl surfaces to the region of the dischargenozzles. It should be noted that at the transverse rotor plane passingthrough the outlets of feed ducts 51, where solid-particle flowlines R-lintersect overflow conduits 35 (FIGURE 4), the conduits occupy only asmall portion of the circumference of the rotor bowl as clearly shown inFIGURE 2. In this way, almost all of the coarse solids will passoutwardly and upwardly through the shallow separating spaces 36a (FIGURE3) underneath the sector-shaped tubes rather than impinging on theoverflow conduits.

Some medium sized particles as well as fines may travel further up intothe separating chamber to the region where the separation of the twoliquid fractions is taking place. These particles will be divertedeither directly or after further separating act-ion in discs 53 towardthe conical bowl surfaces. As indicated by respective flowlines R4 andR-3, a portion of these particles will settle against the inwardlyfacing surfaces 42a of the sectorshaped tubes and will slide outwardlyto fall off the inner lip 43 directly toward nozzles 12a Well clear ofthe actual inlet 44 of the overflow tube. At the same time, as indicatedby flowline R-5, intermediate fraction liquid is diverted around innerlip 43 into inlet 44 due to the established hydraulic balance in thesystem.

Additionally, a clarifying action takes place in space 36a under thesector-shaped tubes in the sense that a layer of the intermediate liquidforms at and moves out along the underside of the sector-shaped tubes toenter the elongated mouth 44 across the outer lip 41 thereof asindicated by the flowlines R-2 of FIGURE 4.

The sector shape of overflow tube 38 so increases the cross-sectionalarea of inlet 44 as compared to the crosssectional area of the circularportions of the overflow conduits that the resultant reduced velocity inconjunction with the shallowness of the inlet promotes laminar flowconditions in the inlet and between plates 40 and 42. This low velocityflow substantially reduces entertainment of solids in the overflow.

However, if any solids are entrained at inlet 44, a quasiseparating-disceffect Within overflow conduit 35 will tend to separate such solidswithin the fan-shaped tube and to return them to the nozzles. That is,sector-shaped plates 40 and 42 are so spaced from each other and are ofsuch extended width that they separate the solids from the intermediateoverflow liquid in a manner similar to the separation effected by discs53. The rejected solids are separated and returned to the nozzles asindicated by flowlines R-6 (FIGURE 5).

From the foregoing it will be seen that the invention provides a novelarrangement and combination of parts preferrably in a three-productcentrifugal machine although not necessarily of the type shown. Theinvention effects improved separating flow condition in the rotor bowland a diversion of potential carry-over solids away from theintermediate liquid fraction inlets. That is, the invention largelyeliminates those flow conditions involving the interference orintersection of intermediate liquid fraction stream with the stream ofconcentrated solids in the bowl and thereby avoids a conditionencountered in other types of three-product centrifugal machines such atthose which employ the well-known Schneider fractionation or dividerdisc. The invention provides for the peripheral overflow advantages ofthe Schneider disc without incurring any of the disadvantages thereof.

This invention is especially useful in centrifugal machines of aconstruction where the Schneider fractionation disc is structurallyinapplicable as in an integral doublecone-shaped rotor bowl where theSchneider disc as a Whole is not insertable through the constricted end.In

contrast, the removable individual sector-shaped overflow conduits ofthis invention are capable of being introduced through the constrictedend of an integral double-cone bowl for mounting substantially in themanner set forth above. This permits the use of the integral bowl in adouble overflow machine with the attendant advantages thereof. I

The invention further provides a sharper liquid-liquid separation due tothe peripheral extent of the intermediate overflow inlets and thelaminar flow conditions induced therein. Accordingly, benefits andadvantages will accrue from the invention in a liquid-liquid separationalone, that is, without a separation of a solids-carrying underflow.

It will be understood that each of the elementsof the inventiondescribed above, or two or more together, may find useful application inother types and constructions of centrifugal machines differing from theone herein described and exemplified. While the invention has beenillustrated and described as embodied in a double-cone; shaped rotorstructure with the primary and intermediate liquid fractions dischargingfrom respective opposite constricted ends of the bowl and with theunderflow discharging from the peripherally arranged nozzles, it is notintended to be limited to the details shown, since various modificationsand structural as well as operational changes may be made withoutdeparting from the spirit of this invention.

Because this invention may thus be embodied in several forms withoutdeparting from the spirit or essential characteristics thereof, thepresent embodiment is illustrative and not restrictive. The scope of theinvention is defined by the appended claims rather than by thedescript-ion preceding them, and all embodiments which fall within themetes and bounds of the claims or which are their functional orstructional equivalents are therefore intended to be embraced by thoseclaims.

I claim:

1. In a centrifuge rotor having a cone-shaped rotor bowl, peripheralunderflow discharge nozzles in said bowl, primary fraction overflowmeans at the end of said rotor, and an intermediate fraction overflowmeans, the improvement wherein said intermediate fraction overflow meanscomprises:

a. an intermediate fraction overflow outlet at one end of said rotor;

b. means for keeping primary overflow from said intermediate overflowoutlet;

c. closed conduit means having an outlet communicating with saidintermediate fraction overflow outlet and having an intermediatefraction overflow inlet within said bowl, said conduit means at saidinlet being spaced away from the interval bowl surface whereby theentire cross-sectional area of said inlet is separated from said surface,to permit underflow solids to pass along the bowl surface clear of saidd. and means fixedly supporting said conduit within said bowl tomaintain said spaced-away relationship between said inlet and said bowlsurface under the centrifugal forces produced during rotor operation;

2. Apparatus as defined in claim 1: said intermediate overflow inletbeing radially shallow and circumferentially elongated to prevententrainment of solids in the overflow.

3. Apparatus as defined in claim 2: said conduit means including afan-shaped tube terminating in said inlet and having opposed, closelyspaced, sector-shaped walls lying substantially parallel to but spacedaway from the conical internal bowl surface to permit quasi-disc-likeseparation within said fan-shaped tube of any solids entrained in theoverflow.

4. Apparatus as defined in claim 3: the space between said sector-shapedwalls being in the range of about .05 to 0.1 inch.

5. Apparatus as defined in claim 3: the space between said fan-shapedtube and the conical internal bowl surface being in the order of 0.25inch.

6. Apparatus as defined in claim 3: the inner sectorshaped wallextending beyond the outer wall at said conduit inlet to define a lip tocarry solids passing along the external surface of said inner wall clearof said inlet.

7. In the centrifuge rotor having a cone-shaped rotor bowl, feed meanshaving an outlet'within said bowl, underflow discharge nozzles at theouter bowl periphery, a primary fraction overflow means at an end ofsaid rotor bowl, and means defining an intermediate fraction overflowoutlet closed off from the primary overflow fraction, the improvementcomprising means defining a plurality of intermediate fraction overflowconduits having fanshaped inlet portions positioned within said bowl andconnecting portions communicating between said inlet portions and saidintermediate fraction overflow outlet means, said fan-shaped inletportions being positioned substantially parallel to but spaced away froma respective portion of the internal surface of said conical bowlwhereby the cross-sectional area of said inlet is separated from saidbowl surface to permit solids to pass along the internal bowl surfaceunder and clear of said conduit inlet portions and support means tosecure said inlet portions in said spaced-away positional relationduring rotor operation.

8. Apparatus as described in claim 7 said conduit connecting portionsbeing positioned in said bowl to traverse the transverse rotor planethrough said feed means outlet and being relatively narrowcircumferentially of the rotor at said plane whereby underflow solidsfrom said feed means pass directly outwardly to said rotor bowl with aminimum of impingement of the solids on said ends of said rotor and at aradial position outward of the truncated rotor bowl ends, said inletportions being adapted to be separately inserted through a rotor bowlend for removable mounting in said rotor.

10. A centrifuge rotor comprising:

a. an integral, truncated-double-cone-shaped rotor bowl;

b. a primary fraction overflow means at an end of said rotor;

c. means defining a secondary fraction overflow outlet chamber at anaxial rotor end;

(1. and a plurality of secondary overflow conduits connecting with saidsecondary overflow outlet chamber means and having fan-shaped inletportions mounted within said bowl to terminate at radial positionsoutward of the truncated rotor bowl ends, said inlet portions havingshallow elongated mouths oriented to occupy a substantial portion of theperiphery of said bowl, said inlet portions at said elongated mouthsbeing spaced away from the internal rotor bowl surface whereby theentire cross-sectional area of each said mouth is separated from saidbowl surface, and means mounting said inlet portions in said rotor bowlto positively support said portions to maintain said spaced-awayrelationship under the centrifugal loads imposed by rotor operation,said inlet portions being adapted to be separately inserted through arotor bowl end for removable mounting in said rotor. 11. In a centrifugerotor having an integral, truncateddouble-cone-shaped rotor bowl, feedmeans having an outlet within said bowl, underflow discharge nozzles at:

the outer bowl periphery, means defining a primary fraction overflowdarn at one axial end of said rotor, and means defining an intermediatefraction overflow chamber at the other rotor end, the improvementcomprising: a. a plurality of intermediate fraction overflow conduitseach having:

(1) a fan-shaped inlet portion with opposed,

spaced-apart, sector-shaped, parallel walls,

(2) and a relatively narrow connecting portion communicating betweensaid inlet portion and intermediate fraction overflow chamber means;

b. said fan-shaped inlet portions being rigidly mounted in said bowlsubstantially parallel to but spaced from a a respective portion of aninternal conical surface 7 of said bowl whereby the cross-sectional areaof said inlet is separated from said bowl surface-during rotoroperation, said inlet portions terminating in shallow, elongated mouthsoriented to occupy a substantial portion of the periphery of said bowlat a radial position outward of the truncated rotor bowl ends;

c. said respective connecting portions being positioned.

outwardly from said feed means outlet to permit underflow solids fromsaid feed means to pass directly outwardly to slide along the conicalrotor bowl surface under said fan-shaped conduit inlet portions wellclear of said conduit mouths with a minimum of the solids impinging onsaid over-flow conduits;

d. the inner sector-shaped wall of said inlet portion extending beyondthe outer wall at said conduit mouth.

to define a lip to carry any impinging solids clear of the inlet mouth;

e. and said inlet portions being adapted to be separately insertedthrough a rotor bowl and for removable mounting in said rotor.

12. A centrifuge rotor comprising:

a. :a truncated-double-cone-shaped rotor bowl having underflow dischargenozzles at the outer periphery thereof;

b. means defining a primary fiaction overflow dam at one axial end ofsaid bowl;

c. a rotor hub closing the other axial end of said rotor bowl;

d. a rotor shaft connected to said hub and extending through said onerotor 'bowl end;

e. a tubular feedwell extending into said one rotor bowl end in spacedrelation to said primary overflow dam and around said rotor shaft;

f. means defining a centrally located open-ended return chamber adjacentto said hub on the side opposite from said rotor bowl;

g. means defining an annular intermediate fraction over flow chamberaround said return chamber;

h. first closed conduit means connecting said return chamber to saidrotor bowl for introducing fluid to the vicinity of said nozzles;

i. and second closed conduit means connecting said annular intermediatefraction overflow chamber to said rotor bowl for conducting intermediatefraction overflow out of said rotor bowl;

j. said second conduit means including fan-shaped inlet portions withopposed, spaced-apart, sector-shaped, parallel walls fixedly positionedin said bowl substantially parallel to but spaced from a respectiveportion of an internal conical surface of said bowl whereby thecross-sectional area of said inlet portion is separated from said bowlsurface to permit underflow solids from said feedwell to slide along theconical rotor bowl surface under and clear of said fan-shaped inletportions;

k. said inlet portions terminating in shallow, elongated mouths orientedto occupy a substantial portion of the periphery of said bowl.

References Cited by the Examiner UNITED STATES PATENTS 2,917,230 12/1959 Kaldewey 233-14 3,073,516 1/1963 Glasson 233-28 3,080,108 3/1963Jacobson 233-14 3,111,490 11/ 1963 Halbach 23314 M. CARY NELSON, PrimaryExaminer.

H. KLINKSIEK, Assistant Examiner.

1. IN A CENTRIFUGE ROTOR HAVING A CONE-SHAPED ROTOR BOWL, PERIPHERALUNDERFLOW DISCHARGE NOZZLES IN SAID BOWL, PRIMARY FRACTION OVERFLOWMEANS AT THE END OF SAID ROTOR, AND AN INTERMEDIATE FRACTION OVERFLOWMEANS, THE IMPROVEMENT WHEREIN SAID INTERMEDIATE FRACTION OVERFLOW MEANSCOMPRISES; A. AN INTERMEDIATE FRACTION OVERFLOW OUTLET AT ONE END OFSAID ROTOR; B. MEANS FOR KEEPING PRIMARY OVERFLOW FORM SAID INTERMEDIATEOVERFLOW OUTLET; C. CLOSED CONDUIT MEANS HAVING AN OUTLET COMMUNICATINGWITH SAID INTERMEDIATE FRACTION OVERFLOW OUTLET AND HAVING ANINTERMEDIATE FRACTION OVERFLOW INLET WITHIN SAID BOWL, SAID CONDUITMEANS AT SAID INLET BEING SPACED AWAY FROM THE INTERVAL BOWL SURFACEWHEREBY THE ENTIRE CROSS-SECTIONAL AREA OF SAID INLET